The present invention relates to a semiconductor power device, particularly a thyristor or gridistor, and to a method of fabricating such a component.
Two kinds of grid structures are known for semiconductor power devices, namely the surface grid structure and the buried grid structure (see IEEE Transactions on Electron Devices, Vol. ED-27, No. A, Nov. 1980, pages 2141 to 2145). To fabricate the semiconductor power component with a buried grid structure, an n.sup.- doped semiconductor material, such as a silicon wafer, is provided on its surface with a masking layer produced by thermal oxidation. Windows are etched into the marginal areas of the wafer, through which the connections for the grid are produced by planar boron diffusion. At the same time, within the same boron diffusion cycle, a p.sup.+ anode is produced on the underside of the wafer. Thereupon a pattern corresponding to a metallic grid mask is produced by etching of the oxide mask in the active area of the wafter. The grid is then produced at the wafer surface by boron diffusion between the bars of the grid. Further, a window is etched out of the oxide mask, substantially above the entire area of the surface grid structure thus formed, in which an n.sup.+ doped layer is grown thereover by silicon liquid phase epitaxy. A buried grid structure is thus obtained in the semiconductor wafer. In further working steps, the not yet covered peripheral areas of the grid structure are provided with conducting connections by contact metallization.
With this prior art method, for example, during the fabrication of a gridistor, a contradoped conductive grid, by vacuum tube analogy, is introduced into the semiconductor. A plurality of masking and etching operations is needed for this purpose, since epotaxy requires an array of contradoping material on the semiconductor surface and a subsequent growth of the basic material thereover by further epitaxy, to transform the array into a buried grid structure. The prior art method requires too many working steps, and is therefore very expensive.